Synchro-tie unit



Nov. 11, 1941. R. w. SCHUCK 2,

SYNCHRO-TIE UNIT Filed Nov. 29, 1939 WITNESSES: INVENTOR 65.4 fiymoflah/fic/n/cm /2 M a v ATTORNEY Patented Nov. 11, 1941 UNITED STATES PATENT OFFICE SYNCHRO-TIE UNIT Pennsylvania Application November 29, 1939, Serial No. 306,712

Claims.

My invention relates to a brush assembly which is useful for electric machines such as motors, generators, synchro-tie units, and the like.

The brushholder in accordance with my invention is particularly adapted for use in synchro-tie units, which units consist of a transmitter and receiver to operate, for example, the steering gear mechanism of destroyers, air craft carriers, cruisers, or the like.

In the conventional types of brush assemblies, the brush is usually carried in a brush box which fits snugly therearound so as to permit radial movement but allow little side play. As the result of this snug fit, it has been experienced in the past that corrosion, even to a small degree, would freeze the brush to the holder, thus breaking contact of the brush with respect to the slip ring (or commutator). Furthermore, the conventional type of brush box has been more complicated and expensive than necessary, including hinged joints and the like.

An object of my invention is to provide a. brush assembly which is so designed as to eliminate the possibility of freezing of the brushes to any part of the assembly, thus avoiding the detrimental effect of separation of the brush from the commutator, slip ring, or other current carrying means on a rotor of an electric machine.

Another object of my invention is to provide a brush assembly which is extremely simple, having a minimum number of parts, which is easy to manufacture but yet which is extremely reliable in operation.

Other objects and advantages will become more apparent from a study of the following specification when considered in conjunction with the accompanying drawing, in which:

Figure 1 is a longitudinal view, partly in cross section, showing a brush assembly in accordance with the teachings of my invention as applied to a synchro-tie unit (partly shown);

Fig. 2 is a cross sectional view taken along the line II of Fig. 1 showing the front of the brush assembly; and

Fig. 3 is an enlarged cross sectional view of the brush and holder taken along the line III-III of Fig. 2.

Referring more particularly to Figs. 1, 2 and 3, numeral denotes an end bracket which forms a portion of the frame structure of an electrical machine, for example, a synchro-tie unit, which end bracket has an opening 2. In registry with opening 2 there is a brush assembly comprising a plurality of pairs of brushes, each pair being shown more clearly in Fig, 2. In registry with opening 2 there is provided a support member 3 which is fastened to the end bracket. A rotor 4 having at the periphery thereof current conducting means, such as a commutator, slip ring, etc. is provided. Three brush units or pairs are shown in Figs. 1 and 2, although it is to be understood that any number of pairs may be used instead. As shown more clearly in Fig. 2, each brush unit comprises a pair of double, semielliptic springs 5 and 6, each spring having one .end thereof rigidly bolted down, with the other spring of the pair by means of a bolt 1. The bolt 1 secures the upper ends of springs 5 and 6 to an insulating member 8 which, in turn, is secured to support 3 by means of bolts I! and I8. A bearing cap H is secured to a portion of end bracket I. Rigidly secured to bearing cap H by means of bolts l2 are plates 13 and Mia of insulating material, which plates have on their inner surface a plurality of grooves or tracks [4 and Ma, respectively, along which are adapted to slide the lower end portions of springs 5 and 6. A pair of brushes l5 and I6 are rigidly secured to substantially the midportion of springs 5 and 6, respectively. The springs 5 and 6 are flexed in such manner as to continuously urge the brushes l5 and I6 radially inwardly into frictional contact engagement With a slip ring on the periphery of rotor 4. This radially inward movement of the brushes is effected by virtue of the reaction of insulating plates l3 and Ho with respect to the lower or free ends of springs 5 and 6, respectively.

In the operation of the device, it will be observed that as the brushes I5 and I6 wear, the lower ends of springs 5 and 6 will slide upwardly within the grooves or tracks l4 and Ma so as to assume a new position and to continuously urge the brushes radially inwardly so as to automatically compensate for wear thereof.-

Another aspect of my invention is the accessibility and ready removability of the brush assembly when it is necessary to replace it. The operator inserts his hand through opening 2 and unscrews single bolt 1 if only one pair of brushes is to be removed or unscrews the bolts H and I8 of support 3 if the entire assembly, which is all that is necessary to completely disengage the brush units from the remainder of the structure. For example, after bolts I1 and I8 are unscrewed, the entire assembly is pulled out, and the lower ends of springs 5 and 6 merely slide along grooves 14 and Ma until they completely emerge from the upper portions thereof. Likewise, in replacing with a new brush assembly, the reverse operation is extremely simple, it being necessary merely to hold the lower ends of springs 5 and 6 compressed before inserting them in respective grooves.

I am, of course, aware that others, particularly after having had the benefit of the teachings of my invention, may devise other devices embodying my invention, and I, therefore, do not Wish to be limited to the specific showings made in the drawings and the descriptive disclosure hereinbefore made, but wish to be limited only by the scope of the appended claims and such prior art as may be pertinent.

-I claim as my invention:

1. A brush assembly for rotating electrical apparatus comprising, in combination, a frame structure having a slotted portion, a leaf spring having one end rigidly secured to a portion of said frame structure and the other end being free and located within said slotted portion, a cover member for said slotted portion having an inner surface which'acts as a bearing for sliding movement of said free end of the leaf spring, and a brush rigidly secured to an intermediate portion of said leaf spring.

2. A brush assembly for rotating electrical apparatus, comprising, in combination, a frame structure having slotted portions, a plurality of pairs of leaf springs in coextensive relationship. each having one end rigidly secured to a common portion of said frame structure and the other end being free and slidable within one of said slotted portions, a cover member having an inner surface which acts as a bearing for said free end in its sliding movement and which effects tensioning of said springs, each spring also having a brush rigidly connected thereto intermediate the ends thereof.

3. In combination with an electric machine having a frame structure, a groove in said frame structure, and a rotor which carries current conducting means on its periphery, a brush assembly comprising a leaf spring having one end rigidly secured to a portion of said frame and the other end free but adapted to slide within said groove} a readily detachable cover member for said groove having a lower smooth surface which acts as a bearing for said free end in its sliding movement, and a brush rigidly secured to a mid- 1 portion of said spring and adapted to be frictionally held against said current conducting means by virtue of the tension of said spring.

4. In combination with an electric machine having a frame structure and a rotor which carries current conducting means on its periphery, a brush assembly comprising a pair of leaf springs, each spring having a brush rigidly secured to its mid-portion, supporting means rigidly securing one end of each of said springs, a pair of insulating track members rigidly secured to said frame structure at circumferentially spaced portions of said rotor, the other ends of said leaf springs being free and adapted to be held radially inwardly by said tracks solely by virtue of frictional .contact therewith, said free end of said springs being slidable along said track under the tension of said springs as the result of wear of said brushes thereby automatically moving said brushes radially inwardly against said current conducting means so as to compensate for wear.

5. In combination with an electric synchro-tie unit having a frame structure including an end bracket and a rotor which carries current conducting means on its periphery, a brush assembly comprisinga plurality of pairs of leaf springs in coextensive relationship, each spring having a brush rigidly secured to its mid-portion, supporting means rigidly securing one end of each of said springs, a bearing element forming a portion of said end bracket and encircling a portion of said rotor, a plurality of pairs of readily detachable track members rigidly secured to said bearing element at circumferentially spaced portions thereof, the other ends of said leaf springs being free and adapted to be held radially inwardly by said tracks by virtue of frictional contact therewith, said free end of said springs being slidable along said track under the tension of said springs as the result of wear of said brushes thereby automatically moving said brushes radially inwardly against said current conducting means so as to compensate for wear.

RAYMOND W. SCHUCK. 

